The present invention relates generally to automatic image enhancement in connection with registration of moving images of a sports scene. More particularly the invention relates to a system according to the preamble of claim 1 and a method of producing a video signal according to the preamble of claim 10. The invention also relates to a computer program according to claim 22 and a computer readable medium according to claim 23.
Recording and broadcasting of sporting events is becoming an increasingly important market area, and therefore the competition is intensified to provide the viewers with satisfying experiences of such events. However, in some sports it is difficult to adequately reflect all important aspects of the game, for instance in a TV transmission. Golf and baseball are two examples of sports wherein a relatively small ball often travels over a comparatively large distance during a short period of time. Due to the technical limitations of the transmission medium and the cameras used it may be problematic for the viewers to follow the balls' path, and thus fully appreciate the sportsmen's performances.
In golf, for example, already after 30 to 70 meters flight an outgoing ball becomes so small that it is equivalent to less than one pixel of a conventional TV screen. Of course, this renders it very difficult to distinguish the ball, particularly if the white ball moves in front of a bright sky. In most cases, the sky is brighter than the rest of the image, i.e. the golfer/batter and the background. Therefore, a correct exposure of the golfer/batter results in an overexposure of the sky, which means that the sky may be represented by an almost saturated white color against which a white (and possibly likewise over exposed) ball easily “disappears”. Therefore, at least in video recordings/transmissions of some scenes/situations of the game, it is highly desirable to augment the visual impression of the ball.
The U.S. Pat. No. 5,489,099 describes a golf ball tracking apparatus having a video camera for producing data representative of a golf ball, and a video frame processor for determining the golf ball image position within a video frame of the camera. Thereby, the camera may be controlled to automatically follow the movements of the ball, i.e. track the actual flight of the ball through the air.
The U.S. Pat. No. 6,233,007 discloses a solution by means of which it is made possible to track balls, pucks and the like with a camera. Here, empirical color data about the ball is used together with estimated motion vectors to identify a ball trajectory. This, in turn, serves as a basis for following the ball's movements via one or more cameras.
The U.S. Pat. No. 5,953,056 describes a system which enhances the display of a sporting event by tracking a moving ball. Overlay video images are here produced which illustrate the ball path, and the overlay images are successively overlaid a background video image representing the sports scene, such that the viewer easily can follow the ball path.
The U.S. Pat. No. 5,912,700 discloses a system for enhancing the TV presentation of an object (i.e. the ball or puck) in a sporting game, wherein one or more sensors in the object are used. Aided by the sensor(s) a processor associated with the TV camera determines the location of the object, and as a result, the TV signal can be edited or augmented to enhance the presentation of the object.
Although the above-mentioned solutions may improve the viewer 's experiences of certain broadcast and/or recorded sporting events important problems remain to be solved in order to render the image enhancement more efficient, reliable and robust. Namely, either an initial manual identification of the ball is required, or sensors/transducers in the ball are required to enable the tracking thereof. However, it may be difficult to accomplish a manual identification with sufficient accuracy within the time available therefore. Moreover, for cost reasons it is generally desirable to reduce the amount of manual intervention as much as possible. On the other hand, any inclusion of sensors or transducers in the ball risk to influence the game itself, at least on a psychological level. Consequently, this is unacceptable, or in any case highly undesirable.